The field of the invention relates to a system and method for ensuring the availability of a storage system.
Computer systems are constantly improving in terms of speed, reliability and processing capability. Consequently, computers are able to handle more complex and sophisticated applications. In a typical computer system environment, several servers are connected to a number of client sites by way of a network. A storage system or device is also connected to the servers via the network to enable the servers to access the storage system. One typical storage system includes a disk array (e.g., a Redundant Array of Independent Disks (“RAID”)) and a disk array controller coupled to the disk array via one or more interface buses such as a small computer system interface (“SCSI”). See U.S. Pat. No. 5,664,187. In networks today, storage is increasingly carried out at great distances from the source of the request. Storage reliability and availability are always a concern. “Availability” is the ability to ensure continued operation of the system in the event of a failure. Typically, data availability is provided by means of redundancy data stored in another location. However, failure of certain system components could be catastrophic. That is, storage availability is nonexistent.
In the event that a SCSI controller fails in a network for example, access and hence data availability (stored or redundant) is lost. In an effort to avoid this problem, a second SCSI controller has been used to access the same storage system or another. In this implementation, each host server employs a “fail over” or “high availability” driver for each operating system used. High availability drivers are used to provide or manage the different paths to access the data desired. The high availability drivers however have drawbacks.
Since high availability drivers are designed specifically for each operating system, the drivers require a large degree of support to ensure that they operate properly with every operating system. The support is labor intensive and expensive. Further, every time an operating system changes (upgrade or version), the current drivers must be tested and modified, if necessary, to ensure that the drivers operate properly with the upgrade or version change. This process is expensive and never ending.